Parental Report of Outdoor Playtime as a Measure of Physical Activity in Preschool-aged ChildrenFREE

From the Divisions of General and Community Pediatrics (Drs Burdette and Whitaker) and Cardiology (Dr Daniels), Cincinnati Children's Hospital Medical Center, and the Department of Pediatrics, University of Cincinnati College of Medicine (Drs Whitaker and Daniels), Cincinnati, Ohio. Dr Burdette is now with the Division of Gastroenterology and Nutrition, The Children's Hospital of Philadelphia, Philadelphia, Pa.

ABSTRACT

BackgroundKeeping young children physically active is an important strategy to promote their health and well-being. To our knowledge, survey measures of physical activity in preschool-aged children are unavailable. Time spent playing outdoors is a potential surrogate measure of physical activity in preschoolers, but parental-report measures of outdoor playtime have not been evaluated.

ObjectiveTo compare a direct measure of physical activity in preschool-aged children with 2 parental-report measures of children's outdoor playtime.

Main Outcome MeasuresThree days of recording with a 3-dimensional accelerometer were used to directly measure physical activity in 250 preschool-aged children. We calculated each child's average vector magnitude per minute while awake. Parental report of outdoor playtime was measured in 2 ways: (1) the score from a checklist used to record outdoor playtime over 3 days and (2) a recall of the usual minutes of daily outdoor playtime during the prior month. We calculated Spearman rank correlation coefficients among these 3 measures.

ResultsThe mean age of the children was 44 months, 87.7% were white, and 12.3% were black. Parents reported that their children spent a mean (±SD) of 146 (±113) minutes playing outdoors each day. Physical activity as measured by the accelerometer was significantly correlated to the time spent playing outdoors, as measured by the checklist (r = 0.33, P <.001) and recall (r = 0.20, P = .003).

ConclusionParental-report measures of outdoor playtime were significantly correlated to a direct measure of physical activity in preschool-aged children, and are worthy of future evaluation as a survey measure.

Figures in this Article

Because the prevalence of obesity is increasing even among preschool-aged children,1 there is a need to begin obesity prevention efforts at young ages. This includes increasing physical activity levels in preschoolers. Unfortunately, instruments to measure physical activity in preschool-aged children are lacking.

Direct measures to assess physical activity, such as observation and accelerometers, are often not feasible in large epidemiologic studies. Therefore, survey measures of physical activity are needed. Adolescents and adults can customarily self-report their physical activity levels, but preschool-aged children are not cognitively capable of recalling their own activity type, duration, or intensity. This is analogous to the inability of children this age to recall sufficient details of their dietary intake for a valid assessment of their diet by self-report.2,3 Thus, to obtain survey data on physical activity in preschoolers, one must rely on proxy reports from parents or other adult caretakers.

Physical activity in preschool-aged children usually occurs during free play rather than during structured activities, and this play consists of short intermittent bouts of activity with frequent rest periods.4 Children's physical activity lacks the sustained periods of systematic movement that characterize adults' physical activity and is, therefore, extremely difficult to measure using conventional survey methods. For all these reasons, there is interest in developing a surrogate measure of physical activity for preschool-aged children that can be reported by a child's parent or other adult caregiver. In prior studies5,6 in which physical activity in preschoolers was measured by direct observation, time spent outdoors was the single strongest correlate of physical activity. Despite this research suggesting that outdoor playtime may be a useful surrogate measure of physical activity, to our knowledge, there are no validated parental-report measures of the time their preschool-aged child spends playing outdoors.

A validated surrogate measure of preschoolers' physical activity, such as parent report of outdoor time, will assist future research efforts and may also be useful to health professionals who are increasingly concerned about obesity prevention counseling and who are in need of tools to assess physical activity levels in their young patients. This study develops and validates 2 parental-report measures of the time preschool-aged children spend playing outdoors—a 3-day record and a 1-month retrospective recall. These 2 measures were compared with a direct measure of physical activity obtained from accelerometers.

METHODS

SUBJECTS

This cross-sectional study, conducted between July 2000 and June 2001, was performed on 250 preschool-aged children recruited from the Cincinnati metropolitan area. To be eligible for the study, children had to be free from any chronic medical condition that affected their growth and development. Subjects were recruited primarily through brochures that were distributed in pediatric offices and in day care centers in the Cincinnati metropolitan area. In addition, advertisements for the study were placed in community newspapers and parents of enrolled children also told their friends about the study. The Institutional Review Board at Cincinnati Children's Hospital Medical Center approved the study.

STUDY MEASURES

Accelerometer

Direct measurement of physical activity was made for each child using a 3-dimensional accelerometer (RT3 Tri-axial Research Tracker; Stayhealthy, Inc, Monrovia, Calif). This small lightweight device (7.1 × 5.6 × 2.8 cm and weighing 65.2 g) was worn around the child's waist like a beeper and collected data on acceleration in 3 planes of movement: mediolateral, anteroposterior, and vertical. It collected this motion data as minute-by-minute counts and then provided a composite score, termed the vector magnitude, that summarized movement in all 3 directions. These data were stored internally by the device and were downloaded to a computer after the monitoring period. The parents of the children in the study were instructed to have the child wear the activity monitor from morning awakening until bedtime on 2 weekdays and 1 weekend day, removing it only for swimming, bathing, and naps. Minutes of recording in which there was a value of 0 vector magnitudes on at least 2 of the 3 planes of movement were considered to be nap times, and these data were excluded.

Outdoor Time Checklist

A 2-question checklist that allowed parents to record the amount of time their child spent playing outdoors each day was developed (Figure 1). Each question focused on the location where outdoor play occurred. Responses to these questions were meant to be mutually exclusive and to include all of the children's outdoor time. The day was divided into 3 separate periods—wake-up time until noon, noon until 6 PM, and 6 PM until bedtime. The amount of time spent playing outdoors during these 3 periods was divided into 5 response options: 0, 1 to 15, 16 to 30, 31 to 60, and more than 60 minutes. The checklist was completed by the parent on 2 weekdays and 1 weekend day, corresponding to the days on which the accelerometer was worn. The parents were not informed that a specific question in the study was to compare the checklist and accelerometer measures.

Outdoor Time Recall Questions

Two questions asked parents to recall the amount of time their child "typically" spent playing outdoors each day in the last month—one question about weekdays and the other about weekend days (Figure 1). The parents recorded how many hours and minutes their child spent playing outdoors. These 2 outdoor time recall questions were adapted from similar questions in the National Longitudinal Survey of Youth7 that ask parents to recall how much time their child spent viewing television (TV). The parents completed these questions when they returned the accelerometer. Therefore, the time frame of these recall questions (the last month) included the 3 days on which the accelerometer was worn by the child and on which the parents recorded outdoor playtime on the checklist.

We conducted cognitive interviews on these 2 questions using a 60-minute focus group with 6 mothers of preschool-aged children. These mothers reported that their children's gross motor play occurred primarily outdoors and that it was easier to quantify outdoor time than to quantify the amount of time their child spent in active gross motor play. We then attempted to understand how these mothers interpreted outdoor time and to identify the most appropriate time frame for recording responses (hours, minutes, or fractions of hours). The outdoor time recall questions were then pilot tested with 15 additional mothers. During the pilot testing, there was another opportunity to probe respondents about how they understood the questions.

ADDITIONAL VARIABLES

Television viewing time was also measured because it has been used in other studies as an indirect measure of physical activity and as a proxy measure for sedentary activities. The measure of TV viewing time was obtained from 2 TV time recall questions that were used in the National Longitudinal Survey of Youth.7 They asked about the amount of time the child spends watching TV or videotapes on a typical weekday and on a typical weekend day. The parent also provided demographic information, such as the age, sex, and race of the child.

COMPUTING STUDY VARIABLES

The accelerometer data were used to derive a single summary measure of physical activity—average vector magnitude per minute while awake. To derive this measure, we first excluded raw data from the accelerometer that corresponded to the time the children were napping. We then calculated the average vector magnitude per minute while awake on each monitoring day. No day was included for an assessment unless there were 8 or more waking hours of monitoring. To analyze the 2 questions on the outdoor time checklist, responses from the 5 time interval categories were coded as 0 through 4 (0 for 0 minutes, 1 for 1-15 minutes, 2 for 16-30 minutes, 3 for 31-60 minutes, and 4 for >60 minutes). Using these ordered categorical responses and summing the responses across both questions gave a maximum score of 24. The responses to the 2 outdoor time recall questions were converted to minutes. For all 3 measures, there were no significant differences between weekday and weekend values, so the mean of these 2 values was computed for each measure.

In summary, we had 3 variables for the data analysis: (1) from the accelerometer, the average amount of activity (vector magnitude per minute) while awake; (2) from the outdoor time checklist, the average daily score (possible range, 0-24); and (3) from the outdoor time recall questions, the average daily time (in minutes) spent playing outdoors. All 250 children had data available from the accelerometer and the outdoor time checklist, but only 214 of the children had data available from the outdoor time recall questions.

DATA ANALYSIS

The association between each of these 3 measures was assessed using Spearman rank correlation coefficients because the checklist data were rank scores. As another method of evaluating the association between the 3 measures, we divided the children into quartiles based on their level of physical activity, as assessed by the accelerometer, and compared the 2 outdoor playtime measures across each quartile of children. We also determined whether our 3 measures differed by season or child sex. For the seasonal analysis, spring was defined as the months of March, April, and May; summer as June, July, and August; autumn as September, October, and November; and winter as December, January, and February. Finally, the 3 primary study variables were compared with TV viewing time. Data from the TV viewing time questions were handled in a similar manner as data from the outdoor time recall questions, generating the average daily time (in minutes) spent watching TV.

RESULTS

The mean age of the 250 children was 44 months (range, 29-52 months). Of the children, 57% were boys, 87.7% were non-Hispanic white, and 12.3% were non-Hispanic black. Data on outdoor playtime (in minutes) and on physical activity (in vector magnitude per minute) had a normal distribution (data not shown). Children spent a mean (±SD) of 146 (±113) minutes per day playing outdoors (Table 1). The average outdoor playtime, by the recall and checklist measures, differed by season. The highest levels of outdoor playtime occurred in the summer; and the lowest, in the winter. The tendency for greater outdoor playtime in the fall than in the spring is consistent with the lower amount of precipitation and the higher temperatures in the Cincinnati fall. Seasonal differences in physical activity levels, as measured by the accelerometer, were less pronounced than for the other 2 measures of physical activity. Boys had significantly higher physical activity levels than girls, but scores for the 2 outdoor playtime measures did not differ significantly between boys and girls.

The time spent playing outdoors, as measured by the checklist, was significantly correlated to the direct measure of physical activity from the accelerometer (r = 0.33, P <.001), as was outdoor playtime measured by recall (r = 0.20, P = .003). The 2 measures of outdoor playtime were also significantly correlated to each other (r = 0.57, P <.001). We also compared outdoor playtime in 4 groups of children categorized by quartile of physical activity level (Table 2).

These preschool-aged children watched a mean (±SD) of 133 (±79) minutes of TV or videotapes a day. The average TV time was significantly inversely correlated to the direct measure of physical activity by accelerometer (r = −0.16, P = .02) and to the amount of time spent playing outdoors by checklist (r = −0.19, P = .005), but not to the recall measure of outdoor playtime (r = −0.01, P = .91).

COMMENT

Our goal was to conduct a study comparing 2 parental-report measures of outdoor playtime in preschool-aged children—a 2-question checklist and 2 recall questions—with a more objective measure of physical activity in children obtained by a 3-dimensional accelerometer. Both measures of outdoor playtime were significantly correlated to the accelerometer measure, with the checklist having the higher correlation. There are 2 potential explanations for the higher correlation with the checklist. First, the checklist may have allowed mothers to provide a better assessment of total outdoor time because of its prompts for time of day, place, and duration of activity. Second, the checklist was completed on the same days as the accelerometer was worn.

The correlation coefficients in this study are of similar magnitude to those obtained in the only other study in which outdoor time was correlated to a measure of physical activity in preschoolers. Klesges et al5 measured outdoor time and physical activity in preschoolers by direct observation, and reported a correlation between these 2 measures of 0.34. Baranowski et al6 also measured outdoor time and physical activity in preschoolers by direct observation, and showed higher activity levels outdoors than indoors. However, they did not report the correlation between these 2 measures.

In older children, other investigators have assessed the correlation between direct measures of physical activity from accelerometers and the scores derived from longer physical activity questionnaires that attempt to assess specific activities. If either a parent completes the physical activity questionnaire8 or the child completes it,9,10 the correlation between the questionnaire scores and the accelerometer measure is also in the range of 0.3 to 0.4.

There are several reasons why the correlations between the outdoor playtime measures and the measure of physical activity from the accelerometer may not have been higher. First, we attempted to quantify a behavioral correlate of physical activity, outdoor playtime, rather than physical activity itself. We did so with the assumption that not all the physical activity of preschool-aged children occurs outdoors and that not all time spent outdoors involves active play. Second, despite the high levels of summer outdoor time, there were relatively low levels of physical activity in the summer, as measured by the accelerometer. This may be because the accelerometers, which were not waterproof, were taken off for swimming and play around water. Finally, the time frame for recalling outdoor play was the past month and the few days that month on which the accelerometer was worn may not have been representative of the month's outdoor playtime.

Despite finding only a moderate correlation between parental-report measures of outdoor playtime and direct measures of physical activity in preschoolers, we believe that the measurement of outdoor play in preschool-aged children is worthy of future evaluation as a research and a clinical tool. Where research is concerned, to our knowledge, there is no alternative questionnaire measure of physical activity in preschoolers. If researchers are to evaluate population-level trends in physical activity in preschool-aged children or to conduct large-scale interventions in children this age, then there needs to be a way to measure physical activity in large groups. This study presented a possible new method.

Because of the epidemic of childhood obesity, health care professionals are making increasing efforts to counsel children and families about physical activity. All the challenges faced by researchers in characterizing physical activity in preschoolers are also faced by clinicians in trying to assess physical activity levels in preschoolers as part of a health behavior inventory. This study shows that asking parents about outdoor playtime is an acceptable surrogate measure of activity in preschoolers given that few alternative interview questions have been suggested for clinical practice11 and that none, to our knowledge, have been compared with a direct measure of physical activity. Furthermore, asking parents about outdoor playtime may be useful in achieving the twin goals, recently recommended by the American Academy of Pediatrics,12 of reducing TV viewing time and increasing unstructured play. In this study, outdoor playtime measured by the checklist was inversely correlated to TV viewing time. Reallocating children's time from TV viewing to outdoor play may not only protect against obesity but may also lead to other beneficial effects on children's well-being, including increased opportunities for enhanced cognitive stimulation through social interaction and imaginative play.

WHAT THIS STUDY ADDS

Physical activity in preschool-aged children is important for their health and well-being, but, to our knowledge, there are no parent-report measures of physical activity available for this age group. Such measures are needed for use in research and clinical practice. This study compares 2 parental-report measures of outdoor playtime with a more direct measure of physical activity by accelerometer.

Both parental-report measures of outdoor playtime—a 2-question checklist and 2 recall questions—were significantly correlated to physical activity. This study presents a surrogate measure of physical activity in preschoolers that can be used when direct measurement is not feasible.

This study was supported by grant R01HL/DK64022 from the National Institutes of Health, Bethesda, Md.

This study was presented in part at the Pediatric Academic Societies Annual Meeting; May 5, 2003; Seattle, Wash; and at the American College of Sports Medicine Annual Meeting; May 31, 2003; San Francisco, Calif.

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